1. Field of the Invention
The present invention relates to a display device using an organic EL element and a control method for recovering performance of the organic EL element.
2. Description of the Related Art
In recent years, since an organic EL (Electro Luminescence) element (hereinafter referred to as luminescence element or simply element) that is made of an organic material enables thin and lightweight display devices and high-speed responses by taking advantage of thin-film self luminescence in which recombination of electrons and holes is performed in an organic layer that is a component material, the organic EL element has attracted attention as a luminescence element used in thin display devices with high picture quality and high performance.
However, in the organic EL element at a time of driving, since many traps affecting electrons and holes of carriers reduce the carriers, luminescence efficiency tends to be reduced. Since the trapped carriers elevate a potential barrier for carrier transport, the luminescence efficiency is reduced.
Since the trapped carriers become space charges and prevent carriers for transport from moving, an electric current itself flowing in the element is consequently suppressed.
In addition, since the organic material itself constituting the element is highly resistive, application of a voltage causes an electric charge to be accumulated in the same manner as a capacitor.
Commonly used is a method for applying a reverse bias to the luminescence element in order to remove such an accumulated charge. A depth of a trap level at a time of applying the reverse bias varies depending on a usage condition, a method such as the following disclosed by Patent Reference 1 is employed to perform desirable reverse bias application according to the usage condition.    Patent Reference 1: Japanese Unexamined Patent Application Publication No. 2005-301084.